1. Field of the Invention
The present invention relates to heteronuclear radioisotope nanoparticle of core-shell structure and a preparation method thereof.
2. Description of the Related Art
Radioisotope refers to a matter in which atomic nucleus thereof emits radioactive rays without requiring external influence such as pressure, temperature, chemical treatment, to turn into different type of atomic nucleus. The generally available radioisotope includes 198Au, 63Ni, 110mAg, 64Cu, 60Co, 192Ir, or 103Pd.
In the industrial application, open radioisotope generally serves as a tracer. That is, by tracing radioactive rays emitted from the radioisotope by a measuring device, it is possible to analyze the behavior of a material. Since gamma (γ) ray does not carry electricity nor does it have mass, this has less interaction with the matter and less energy loss when passing through the matter compared to the other radioactive rays. Further, since γ ray has strong penetrating power irradiated from the radioactive nanoparticles, this can penetrate through the wall of the vessel containing the fluid to easily detect the target of detection existing in the fluid.
The metal nanoparticles are generally made by electric bombardment, sodium/halide flame and encapsulation technology (SFE), chemical reduction, or electric reduction. However, the metal nanoparticles made by these methods have rather irregular granularity of the particles, and mass production is rather difficult at room temperature. Meanwhile, the radiation reduction relates to irradiating radioactive ray onto metal ion solution and generating metal nanoparticles using free radicals generated from the solution. This method has the advantages of no side reaction, and mass-productability at room temperature. By way of example, Reference 1 (S. H. Choi et al.) report about fabricating precious metal nanoparticles using radiation reduction, and using these as catalysts. Further, S. H. Choi et al. have conducted a study regarding radioactivation of the nanoparticles by irradiating neutrons thereon. Further, Reference 2 (S. D. Oh et al.) researched about loading precious nanoparticles in a carbon nano-tube to use as a fuel battery, in which the researchers studied about synthesizing nanoparticle alloy.
The researchers of References 1 and 2 used surfactant or soluble polymer as colloid stabilizer or nanoparticles loaded in a specific carrier to stabilize the nanoparticles. However, in fabricating radioactive nanoparticles, there is a risk that the colloid stabilizer itself can be activated. Therefore, it is required that the use of colloid stabilizer be minimized or the stabilizer be completely eliminated after use, in order to use the radioactive nanoparticles as a tracer. However, if the colloid stabilizer is eliminated in the fabricating process of the metal nanoparticles, aggregation can occur among the nanoparticles due to considerably low mass ratio to surface area, and as a result, the nanoparticles grow and cannot serve as a tracer for flow detection of a target of the research. In order to overcome the problem explained above, a technique to coat the metal nanoparticles with SiO2 which is not activated even by the radiation of the neutron (Reference 3).
Meanwhile, Reference 4 (C. P. Winlove et al.) studied about attaching iodine-125 (125I) as radioisotope to gold (Au) nanoparticle and mixing with natural polymer such as protein peptide to use this as a tracer. However, in implementing this to high temperature and high pressure industrial process, there is a problem that the radioisotope (125I) is separated from the gold nanoparticle. Further, Reference 5 (A. V. S. Roberts) and 6 (M. K. Pratten) prepared colloid particles by, first, chelating 125I and 14C to polyvinylpyrrolidone as a stabilizer, and then coupling the result to colloid gold to use it as a bio-tracer. However, since radioisotopes such as 125I and 14C are adsorbed onto soil and emits low energy of radiation, it is difficult to detect the behavior in the soil sample, not to mention the flow in the industrial processing.
Accordingly, considering the fact that the measurement result with a single radioactive particle particularly on the multi phase flow does not provide information about phase ratio, the present inventors prepared heteronuclear radioisotope nanoparticle with core-shell structure in which two different types of elements as the cores are coated with SiO2, to thus obtain information about the phase ratio on the multi phase flow and calculate the volume ratio, and was confirmed that the prepared nanoparticle can be used as a tracer to detect the flow behavior of the fluid, and completed the invention.    [Reference 1] S.-H Choi, Y.-P. Zhang, A. Gopalan, K.-P. Lee, H.-D. Kang, Preparation of Catalytically Efficient Precious Metallic Colloids by γ-Irradiation and Characterization, Colloids Surfaces A, 256, 165-170 (2005).    [Reference 2] S.-D. Oh, B.-K. So, S.-H. Choi, A. Gopalan, K.-P. Lee, K. R. Yoon, I. S. Choi, Dispersing of Ag, Pd, and Pt—Ru alloy nanoparticles on single-walled carbon nanotubes by γ-irradiation, Mater. Lett., 59, 1121-1124 (2005).    [Reference 3] KR 10-2010-0034499 A Apr. 1, 2010, p. 4, lines 19-24    [Reference 4] C. P. Winlove, J. Davis, A. Iacovides, A. Chabanel, Radioactive Gold Colloid as a Tracer of Macromolecules Transport, Biotechnology, 18, 569-578 (1981).    [Reference 5] A. V. S. Roberts, K. E. Williams, and J. B. LLoyd, “The Pinocytosis of 125I-Labelled Poly(vinylpyrrolidone), [14C]Sucrose and Colloidal [198Au]Gold by Rat Yolk Sac Cultured in vitro, Biochem. J. 168, 239-244 (1977).    [Reference 6] M. K. Pratten, and J. B. Lloyd, Effects of Temperature, Metabolic Inhibitors and Some Other Factors on Fluid-Phase and Adsorptive Pinocytosisi by Rat Peritoneal Macrophages, Biochem. J., 180, 567-571 (1979).